Steady state is just that, steady state. It will occur at...

Steady state is just that, steady state. It will occur at variable times.
It clearly occurred within the 10 day period.
There isn't an industry standard for trench length as far as I am aware.

AMN are talking about 250km all up, what makes 12 x 100m representative?
Furthermore it is almost certain that the final feasibility studies will require much longer trenches.
As for grade, it means nothing without flow, evaporation or recovery. Please tell me why a lower grade, in the case of AMN, 40% lower, can ever be an advantage. I am genuinely interested to know.
Cheers